Audit scroll widgets in DevTools to see if notificationPredicate is needed

A [`notificationPredicate`](https://api.flutter.dev/flutter/material/Scrollbar/notificationPredicate.html) is required for scrollbars whose corresponding scrollview is not the first nested scrollview beneath them (see image below for an example where the`notificationPredicate` is needed). DevTools wasn't using `notificationPredicate` before https://github.com/flutter/devtools/pull/3262. We should check to see if it's needed anywhere else.


在 DevTools 代码库中搜索 Scrollbar 和嵌套 scrollview 的使用情况，然后将其与 issue 中链接的 notificationPredicate API 指南进行比较。完成的标准是检查过每个相关的 Scrollbar，并识别和处理所有需要 notificationPredicate 的情况。

由索引模型根据 Issue 内容生成。